1. Field of Invention
This invention relates to the field of metal founding, and more specifically to an apertured strainer means for separating unwanted components from casting material.
2. Description of Related Art
Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand as the mold material. The term “sand casting” can also refer to an object produced via the sand casting process. Specialized factories called foundries produce sand castings. Production of over 70% of all metal parts occurs via a sand casting process such as the DISAMATIC process.
High-volume foundries typically use vertical molding processes such as the DISAMATIC process. Molds form a line allowing pouring of castings one after another. The process blows a molding sand mixture into a molding chamber using compressed air. The process then squeezes the molding sand between patterned plates, each of which ultimately forms half of the pattern of the sand mold. Two sand molds pushed together form a complete internal sand cavity that receives the molten metal.
After squeezing, one of the chamber plates, a swing plate, swings open and the opposite plate, a ram plate, pushes the finished sand mold onto a conveyor. If desired, the process inserts cores into the sand cavity to form holes and recesses in the finished part. The cycle repeats until a chain of finished molds butt up to each other on the conveyor.
During this process, molten metal pours into sand cavities from a receptacle known in the art as a “pour cup” located on the top of each mold and positioned above a channel in the sand mold called the sprue. An automated device called a filter setter places the filter between the pour cup and the sprue inlet. The filter setter moves the filter into position and then injects the filter into the sand mold. The filter print is the area in the sand into which the filter inserts.
It is desirable to decrease the size of the filter print because the filter print and channels entirely fill with metal during the casting process. Metal left behind in the sprue, channels and filter print is excess metal, requiring removal from the part and repurposing.
It is a problem known in the art that repurposing metal recovered from the sprue, channels and filter print is very costly. An important component of a foundry's profitability is its ability to reduce the amount of repurposed metal and the effective “yield” of the metal that goes into the finished part. If a foundry is able to reduce the amount size of a sprue, channels and filter print by 10%, this could increase foundry yield by 2% to 5%.
There several problems associated with filters known in the art. Ceramic and silica filters must be carefully primed or they fracture and introduce fragments in the casting. Ceramic filters are large, requiring correspondingly large filter setters to hold them in place. Ceramic filters are also expensive. Custom sizes and shapes require special manufacturing, making them impractical for small production runs.
One solution is to replace ceramic filters with cloth or mesh filters. Previous attempts to use cloth filters failed because filter setters could not hold the filters in place or because the sand compromised parts used for clamping or releasing the filters. For example, sand can clog or compromise springs and ball bearings capable of securing and quickly releasing the filter. Additionally, ball bearing and spring devices known in the art did not sufficiently support the filter during insertion, resulting in incorrect filter positioning or entanglement with other parts before ejection.
It is desirable to provide a filter setter capable of holding a cloth filter.
It is further desirable to provide a filter setter with an increased resistance to compromise by sand.